A hydraulic cylinder spool valve device, which extends and retracts a cylinder rod of a hydraulic cylinder, includes: a first spool valve having a first dead band and a first opening characteristic; a second spool valve having a second dead band and a second opening characteristic; and a controller performing communication with the hydraulic cylinder by using the first spool valve and positioning the second spool of the second spool valve within the second dead band and performing communication with the hydraulic cylinder by using the second spool valve and positioning the first spool of the first spool valve within the first dead band, and adjusting a characteristic of a switching dead band between the first opening characteristic and the second opening characteristic.

A hydraulic cylinder spool valve device, which extends and retracts a cylinder rod of a hydraulic cylinder, includes: a first spool valve having a first dead band and a first opening characteristic; a second spool valve having a second dead band and a second opening characteristic; and a controller performing communication with the hydraulic cylinder by using the first spool valve and positioning the second spool of the second spool valve within the second dead band and performing communication with the hydraulic cylinder by using the second spool valve and positioning the first spool of the first spool valve within the first dead band, and adjusting a characteristic of a switching dead band between the first opening characteristic and the second opening characteristic.

A valve block arrangement configured as a closed center system includes at least one main spool for controlling a hydraulic consumer. The main spool is configured to open and close at least one pressure medium connection between a hydraulic pump and the consumer in controlled, continuous fashion and, in at least one embodiment, is electrically activated. A bypass flow path with a cut valve branches off between the adjustable, hydraulic pump and the main spool. The cut valve is configured to open and close a pressure medium connection between the hydraulic pump and a tank in controlled, continuous fashion. The cut valve is electrically activatable.

A valve block arrangement configured as a closed center system includes at least one main spool for controlling a hydraulic consumer. The main spool is configured to open and close at least one pressure medium connection between a hydraulic pump and the consumer in controlled, continuous fashion and, in at least one embodiment, is electrically activated. A bypass flow path with a cut valve branches off between the adjustable, hydraulic pump and the main spool. The cut valve is configured to open and close a pressure medium connection between the hydraulic pump and a tank in controlled, continuous fashion. The cut valve is electrically activatable.

A hydraulic spool valve assembly comprising a housing defining a bore having a longitudinal axis (L), a hydraulic spool valve, a sleeve disposed within the bore and a temperature compensation device disposed between the sleeve and the housing. The hydraulic spool valve having a first end for connection to a drive arm, and an opposing second end disposed within the bore. The sleeve disposed between the hydraulic spool valve and the housing. The temperature compensation device configured to expand in a first longitudinal direction in response to a temperature increase, to oppose movement of the sleeve in an opposing second longitudinal direction caused by the temperature increase.

A hydraulic spool valve assembly comprising a housing defining a bore having a longitudinal axis (L), a hydraulic spool valve, a sleeve disposed within the bore and a temperature compensation device disposed between the sleeve and the housing. The hydraulic spool valve having a first end for connection to a drive arm, and an opposing second end disposed within the bore. The sleeve disposed between the hydraulic spool valve and the housing. The temperature compensation device configured to expand in a first longitudinal direction in response to a temperature increase, to oppose movement of the sleeve in an opposing second longitudinal direction caused by the temperature increase.

A readily removable expanding precision holding and locating pin for securing parts to a work surface or assembly. This device works equally well as a threaded in insert with controlled fit counter bore, press fit or controlled fit bore, a taper fit etc. allowing the device to be used in many standard fixtures without modification the fixture, for example, tombstone fixtures mounted on horizontal machining centers. The device itself can be furnished as an oversize mandrel that can be machined to less than 50% of its original diameter. The device holds and can position in the X, Y, Z, directions and also resists rotation along the C/L Axis.

The present disclosure relates to an adjustment system a method for compensating for temperature variations in a spool valve. The spool valve and adjustment system may be parts in a duplex hydraulic actuator. The adjustment device comprises a spring, a pivot point, and a shape memory alloy (SMA) device. The spring and SMA device are disposed on either side of the pivot point to hold the pivot point in a first position. The SMA device is configured to change size in response to a temperature change so as move the pivot point to a second location. This may eliminate force fight in the duplex hydraulic actuator by preventing asynchronous activation of the spool valves due to thermal expansion within the spool valves.

The present disclosure relates to an adjustment system a method for compensating for temperature variations in a spool valve. The spool valve and adjustment system may be parts in a duplex hydraulic actuator. The adjustment device comprises a spring, a pivot point, and a shape memory alloy (SMA) device. The spring and SMA device are disposed on either side of the pivot point to hold the pivot point in a first position. The SMA device is configured to change size in response to a temperature change so as move the pivot point to a second location. This may eliminate force fight in the duplex hydraulic actuator by preventing asynchronous activation of the spool valves due to thermal expansion within the spool valves.

The hydraulic actuator comprises a hydraulic drive cylinder, a first hydraulic output cylinder which is hydraulically coupled to the drive cylinder, and a pressure valve which limits the pressure on the output limiting cylinder depending on an action time of a force on the drive cylinder and/or output piston, wherein the pressure limiting valve is arranged opposite a second output cylinder for limiting pressure and/or in a second output cylinder for relieving pressure, and wherein the second output cylinder is hydraulically coupled to the drive cylinder. The method is a method for operating such a hydraulic actuator, wherein the drive actuator is deflected with deflections having a deflection duration at a deflection frequency for the duration of an acting or a non-acting phase of the hydraulic actuator, wherein the deflection duration defines a movement stiffness of the hydraulic actuator and the deflection frequency defines the resulting deflection speed of the hydraulic actuator.